Both of the new suspects in relation to the Lockerbie bombing were on the radar of investigators ahead of the original trial, a former FBI agent has revealed.

Dick Marquise, who led the US investigation of the bombing, said Abu Agila Mas'ud, suspected of being a bomb technician, was close to being tried along with the man convicted of the bombing Adelbaset Ali Mohmed Al-Megrahi. However prosecutors believed the case against him was not strong enough and decided not to pursue it.

Meanwhile the other man named last week in connection with the bombing, Abdullah al-Senussi, former intelligence chief to Muammar Gaddafi was investigated, but there was no real evidence against him, Mr Marquise said.

Speaking after the Crown Office announced that it was seeking permission to interview two new suspects, Mr Marquise was reported as saying al-Senussi had been in the spotlight because of his seniority. "We had him as a possible suspect," he said. "We had heard stories that he was involved deeply in terrorist plots, but nothing specific in regard to Lockerbie."

Mas'ud, though had travelled with Megrahi in and out of Malta a number of times and evidence placed him in contact with Megrahi on the morning the bomb bag left Malta, MR Marquise said. "We believed he was a technician of some kind - a bomb builder. I think the prosecutors erred on the side of caution," he said.

The new names emerged after Ken Dorstein, brother of Lockerbie bomb victim David, made a documentary suggesting Mas'ud was the bomb-maker. Senussi and Mas'ud are both currently in jail in Libya, with the former facing a death sentence and the latter serving a 10 year sentence for bomb-making.

Sources close to the Scottish Government are said to believe Libyan authorities may never agree to extradite the pair and relatives of victims are pessimistic about the chances of further convictions.

Jane Schultz, who lost her son Tomas, then 20, on the flight, said: "This has been a long time coming. Maybe we might have the complete truth about it. Unfortunately I don't think we will."

Meanwhile Reverend John Mosey, whose 19 year old Daughter Helga was killed in the bombing, warned relatives of those who lost their lives in the shooting down of Malaysia Airlines plane MH17 15 months ago that they may face a similar battle to Lockerbie families to establish the truth."The two things they will need to do is get good lawyers and form together in a strong unit, because there are political implications here, as there were at Lockerbie," he said.